A challenge faced by fabric processors is to produce a fabric having desired characteristics such as water and stain repellence while maintaining both the desired look of the fabric and the tactile feel (“hand”). For fabrics intended for use in high-traffic areas such as restaurants, hotel rooms, hospices, and other such facilities, it is desirable that the fabric be highly resistant to wetting and staining, and be durable. Examples include fabrics used for tablecloths in restaurants, bedding in hospitals, and upholstery in hotels. At the same time, it is desirable that these fabrics be aesthetically pleasing, both to the eye and to the touch.
In addition to being stain repellent, it is also often desirable for a fabric used in high traffic areas to be water repellent and resistant. In this context, the terms “water repellent” and “water resistant” are used interchangeably unless otherwise specifically noted. “Water resistant” is sometimes used to mean that a substance is chemically resistant to the action of water and/or will not be removed by exposure to water. As used herein, “water resistant” and “water repellent” are used to mean the quality of being impervious to water, both as to wetting of the fabric and as to passage of a liquid through the fabric. It should be noted, however, that a fabric that is water resistant need not necessarily also be vapor resistant, and it is often desired that water repellent and resistant fabrics specifically retain vapor permeability.
There are several ways of rendering a fabric water resistant. In some treatments, a fabric may be treated first with a soap and then with metal stearates. Other treatments include the use of silicon compounds such as polydimethylsiloxane. In addition to treatment with stearates, other wax or waxlike treatments have been used such as treatments involving paraffins or ethylene/vinyl acetate copolymers. Examples of these types of coatings can be found, for example, in U.S. Pat. Nos. 4,027,062; 4,833,006; and 4,594,286 and which are incorporated herein by reference. While fabrics prepared according to these disclosures exhibit water resistance, it has been claimed elsewhere that these fabrics have an unacceptable hand and suffer from other problems rendering them unsuitable for use in all situations. See for example, U.S. Pat. No. 6,251,210 and which is incorporated herein by reference.
Other solutions to the problem of finding an acceptable combination of water and stain resistance, durability, and aesthetic qualities have included the creation of synthetic leathers and vinyl (particularly polyvinylchloride) coated fabrics. To date, synthetic leathers have failed to replace genuine leather. Vinyl coated fabrics are very heavy, completely lacking the feel of cloth.
Other attempts to create water and stain resistant fabrics have involved the use of fluorochemicals, exemplified by SCOTCHGARD® (3M Corporation, St. Paul, Minn.). Applications of relatively small amounts of these types of fluorchemical treating agents can render fabrics somewhat resistant to water and stains. To achieve a more complete resistance to these factors requires application of such thick coatings of these agents which impairs the desired look and hand of the fabric.
Several attempts have been made to provide a fabric treated to be water and stain resistant. One example of a method for treating fabrics is found in U.S. Pat. No. 6,541,138, the disclosure of which is incorporated herein by reference. According to the disclosure of this patent, a fabric is rendered stain and water resistant by subjecting it to two treatments, either or both of which may be repeated as desired. According to a first embodiment of this method, the fabric is first treated with a composition minimally comprising a urethane latex, an acrylic latex, a cross-linking resin, at least one antimicrobial agent, and an organic fluorochemical treating agent, such as SCOTCHGARD®. The fabric is then dried and cured at an elevated temperature. The fabric is then subjected to treatment with a second composition. The second composition, according to the patent, likewise requires a urethane latex, an acrylic latex, at least one antimicrobial agent, and a fluorochemical treating agent. The second composition is preferably thicker than the first and is preferably applied using a knife or doctor blade. The coating is dried and cured at an elevated temperature.
Although the fabric resulting from the method as taught above is said to retain the hand and feel of the original fabric while having the desired stain and water resistant qualities, the method has several drawbacks. It is required, for example, that the urethane and acrylic latex compounds be compatible with each other as defined in the patent, thus limiting the choices of latex available. Also, certain fabrics, particularly those with a looser weave, will require additional treatments with the first and/or second treatment compositions. This adds both to the expense of treating the fabric and to the time required to treat the fabric, all with the attendant logistical problems of handling the fabric as it is being repeatedly treated.
A related fabric treatment and process is disclosed in U.S. Pat. No. 6,492,001, the disclosure of which is incorporated herein by reference, and in which the fabric is treated with a first coating solution and is then provided with a polymeric film on one side of the treated fabric. According to this patent, the fabric is treated with an aqueous solution of a fluorochemical, although the solution may include additional components. The treated fabric is then heated to an elevated temperature for a period of time sufficient to cure the coating solution, that is, to dry it and perform any necessary cross-linking. A polymeric film is then attached to one side of the treated fabric. According to the patent specification, the film can be “any curable or cross-linkable polymer, copolymer, blend and the like of polymeric material.” It is disclosed that the film can be attached to the treated fabric in any known manner, such as by use of an adhesive, by direct lamination, or by forming the film directly on the fabric. It is also disclosed that the film may be adhered to the fabric prior to the fabric being treated with the aqueous solution. Using this method of attaching a film to fabric can create the potential of the film and the fabric separating or delaminating during further processing or in actual use.
Perhaps a more problematic drawback to the fabric treatment disclosed in the patents such as the '138 patent and others cited above lies in its requirement of the use of a formaldehyde based cross-lining agent. Such cross-linking agents, including the ones listed as preferred in the specification of the '138 patent, are capable of causing a release of formaldehyde and similar compounds event after the treated fabric has been dried and cured. This off-gassing can continue for an appreciable amount of time. Such off-gassing has been thought to contribute to what is known as “sick-building” syndrome and is therefore avoided by those attempting to create healthier environments. In some usages, such as hospitals, the emission of volatile organic compounds (VOCs) such as formaldehyde is strictly limited. Thus, treatments that use, rely on, or result in residual formaldehyde emission are of increasing limited utility, particularly in the very environments for which they are intended.
There is needed in the art a process for treating a fabric, and a fabric product produced thereby, that results in a fabric that retains its original aesthetic qualities while exhibiting enhanced properties such as durability, wear resistance, and stain and water resistance. Moreover, to protect the environment and avoid the creation of unwanted contaminants, it is desired that the process use no formaldehyde or formaldehydic compounds and that the treated fabric not give off such compounds during its useful life.